KR20120101970A - Electrode for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

PURPOSE: An electrode for a lithium secondary battery is provided to comprise ionomer comprising specific copolymer together with lithium-manganese oxide, thereby capable of improving lifetime performance. CONSTITUTION: An electrode for a lithium secondary battery comprises an active material, and a copolymer comprising a structure unit in chemical formula 1. In chemical formula 1, A is a group selected from -O-(CFRf3- CFRf4)-, -(CFRf5- CFRf6)-, and combinations thereof. Rf1-Rf6 is respectively and independently selected from a group consisting of fluorine, C1-C4 alkyl, and fluorinated C1-C4 alkyl. X and y is respectively and independently an integer from 1-100,000. A content of the copolymer is 0.1-10 parts by weight based on 100.0 parts by weight of the active material.

Description

ELECTRODE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME

It relates to a lithium secondary battery electrode and a lithium secondary battery comprising the same.

A battery is a device that converts chemical energy generated during the electrochemical redox reaction of a chemical contained in the cell into electrical energy. A primary battery that needs to be discarded when all the energy inside the battery is exhausted and a secondary battery that can be charged many times It can be divided into batteries. Among them, the secondary battery may be charged and discharged many times using reversible mutual conversion of chemical energy and electrical energy.

On the other hand, the recent development of the high-tech electronic industry is possible to reduce the size and weight of the electronic equipment is increasing the use of portable electronic devices. As a power source for such portable electronic devices, the necessity of a battery having a high energy density has been increased, and research on lithium secondary batteries has been actively conducted.

In general, a lithium secondary battery electrode is prepared by mixing an electrode active material, a binder, and a conductive agent to prepare a slurry, coating the same on a pole plate, and then drying and rolling the slurry. Conventionally, as the binder, polyvinylidene fluoride or styrene-butadiene rubber is mainly used.

One embodiment of the present invention is to provide an electrode for a lithium secondary battery that can provide a lithium secondary battery with improved life characteristics.

Another embodiment of the present invention is to provide a lithium secondary battery comprising the electrode for a lithium secondary battery.

In one embodiment of the invention, the active material; And it provides a lithium secondary battery electrode comprising a copolymer comprising a structural unit represented by the formula (1).

[Formula 1]

Where

A is selected from the group consisting of -O- (CFR _f3 -CFR _f4 )-,-(CFR _f5 -CFR _f6 ) _-and combinations thereof,

R _f1 to R _f6 are each independently selected from the group consisting of fluorine, C1 to C4 alkyl, and fluorinated C1 to C4 alkyl,

x and y are each independently an integer of 1-100,000.

The structural unit represented by Chemical Formula 1 may be represented by the following Chemical Formula 2.

[Formula 2]

Wherein x is an integer from 3 to 20, y is an integer from 1 to 10, and z is an integer from 1 to 10.

The active material may include a cathode active material.

The cathode active material is a lithium secondary battery electrode comprising a lithium manganese oxide.

The active material may include a negative electrode active material.

The content of the copolymer may be 0.1 to 10 parts by weight based on 100 parts by weight of the active material.

The copolymer may include a material selected from the group consisting of Nafion N1110, Nafion N117, Nafion N115, Nafion NR-212, Nafion NR-211, Nafion XL-100, Nafion NR50 1100 EW, and combinations thereof.

The electrode may include an active material layer including a mixture of the copolymer and the active material.

The electrode may include an active material layer and a coating layer, and the coating layer may be formed by coating the copolymer directly on the active material layer. The active material layer may include a mixture of the copolymer and the active material.

The copolymer may be present so that the concentration of the active material layer is increased toward the interface with the coating layer in the.

The thickness of the coating layer may be 0.1% to 10% of the active material layer.

In another embodiment of the invention, the first electrode formed of the above-described electrode; Second electrode; Separator; And it provides a lithium secondary battery comprising an electrolyte.

The lithium secondary battery has improved life characteristics.

1 is a view schematically showing a lithium secondary battery according to an embodiment of the present invention.
2 is a schematic diagram showing a part of a cross section of a lithium secondary battery including an electrode formed according to another embodiment of the present invention.
3 is a schematic diagram showing a part of a cross section of a lithium secondary battery including an electrode formed according to another embodiment of the present invention.
Figure 4 is a graph showing the high temperature life characteristics of the lithium secondary battery prepared according to Examples 2 to 5 and Comparative Example 2 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

According to one embodiment of the invention, the lithium secondary battery electrode includes an ionomer (ionomer) comprising a copolymer comprising a structural unit represented by the following formula (1). The term 'copolymer' described herein is any type of block copolymer, alternating copolymer, random copolymer, graft copolymer, and the like. Includes all of them.

[Formula 1]

Wherein A is selected from the group consisting of -O- (CFR _f3 -CFR _f4 )-,-(CFR _f5 -CFR _f6 ) _-and combinations thereof, for example, A is -O- (CFR _f3- CFR _f4 )-and-(CFR _f5 -CFR _f6 )-. R _f1 to R _f6 are each independently selected from the group consisting of fluorine, C1 to C4 alkyl, and fluorinated C1 to C4 alkyl, for example, R _f1 to R _f6 are each independently fluorine, CH ₃ and CF ₃ . x and y are each independently an integer of 1-100,000, For example, said x and y may be an integer of 1-100 each independently.

In another embodiment of the present invention, the structural unit represented by Chemical Formula 1 may be represented by the following Chemical Formula 2.

[Formula 2]

Wherein x is an integer from 3 to 20, y is an integer from 1 to 10, and z is an integer from 1 to 10. For example, x may be an integer from 6 to 15, y may be an integer from 1 to 5, and z may be an integer from 1 to 5.

In the structural unit represented by Chemical Formula 2, A is -O- (CF ₂ -CFCF ₃ )] _z-1- [O- (CF ₂ -CF ₂ )]-in the structural unit represented by Chemical Formula 1, and R is _f1 is F and R _f2 is CF ₃ .

Non-limiting specific examples of the ionomer are Nafion N1110 (manufactured by Dupont Co.), Nafion N117 (manufactured by Dupont Co.), Nafion N115 (manufactured by Dupont Co.), Nafion NR-212 (manufactured by Dupont Co.), Nafion NR -211 (manufactured by Dupont Co.), Nafion XL-100 (manufactured by Dupont Co.), Nafion NR50 1100 EW (manufactured by Dupont Co.), and combinations thereof.

According to another embodiment of the present invention, the lithium secondary battery electrode includes a current collector and an active material layer formed on the current collector, the ionomer comprising a copolymer comprising a structural unit represented by the formula (1) is an active material and The mixture may be included in the active material layer.

The electrode may be an anode or a cathode. When the electrode is a positive electrode, the active material layer is a positive electrode active material layer including an ionomer and a positive electrode active material including a copolymer including the structural unit represented by Formula 1, and when the electrode is a negative electrode, the active material layer is represented by Formula 1 It is formed of a negative electrode active material layer containing an ionomer and a negative electrode active material comprising a copolymer comprising a structural unit represented.

For example, the active material layer may be prepared by applying a composition including an ionomer, an active material, a conductive material, a binder, a solvent, and the like including a copolymer including the structural unit represented by Formula 1 above. . In this case, the ionomer including the copolymer including the structural unit represented by Formula 1 may be evenly distributed in the active material layer. FIG. 2 is a schematic diagram showing a part of a cross section of a lithium secondary battery including the electrode thus formed.

In another example, the active material layer is formed by applying a composition containing an active material, a conductive material, a binder, a solvent, and the like on a current collector, and then comprises an ionomer including a copolymer including a structural unit represented by Formula 1 above. The structure represented by the formula (1) in the active material layer by applying a solution containing on the active material layer to the solution containing the ionomer containing a copolymer comprising a structural unit represented by the formula (1) penetrating into the active material layer It is possible to include an ionomer comprising a copolymer comprising a unit.

The thickness of the coating layer formed by applying the solution containing the ionomer may be about 0.1% to about 10% of the thickness of the active material layer. When the thickness of the coating layer formed by applying the solution containing the ionomer is thinner than about 0.1% of the thickness of the active material layer, it is not sufficient to capture water and metal ions such as transition metal ions. If the thickness of the coating layer formed by applying the solution containing the ionomer is thicker than about 10% of the thickness of the active material layer, since it adversely affects the movement of lithium ions, the cell capacity decreases as the electrode thickens. You lose. Since the ionomer including the copolymer including the structural unit represented by Formula 1 in the coating layer penetrates into the active material layer, the concentration gradient of the ionomer in the active material layer increases toward the interface facing the separator. have.

3 is a schematic diagram showing a part of a cross section of a lithium secondary battery including the electrode formed as described above.

The ionomer comprising a copolymer including the structural unit represented by Chemical Formula 1 is a fluorine-based copolymer having a sulfonic acid group, which traps water and a metal, thereby growing a SEI (Solid Electrolyte Interface) film generated on the surface of the cathode. This can be alleviated, and as a result, the life of the lithium secondary battery can be improved.

In evaluating the life of the lithium secondary battery, the larger the capacity reduction, the larger the thickness of the SEI film and the higher the metal content in the negative electrode. The metal in the measured negative electrode is eluted from the positive electrode active material and moved to the negative electrode. Moisture in the electrolyte is one of the causes of metal elution in the positive electrode active material. As such, the metal or the metal oxide that is present in the negative electrode accelerates the growth of the SEI film of the negative electrode to reduce the life of the lithium secondary battery.

The sulfonic acid group of the ionomer including the copolymer including the structural unit represented by Chemical Formula 1 forms a salt by ion exchange reaction with the metal ion eluted from the positive electrode active material, thereby trapping the metal ion and moving to the surface of the negative electrode active material. The amount of metal ions is reduced. For example, in the case of monovalent metals, the reaction of Scheme 1 may occur; in the case of divalent metals, reaction of Scheme 2 is possible (Source: Nasef et al., "Adsorption of some heavy metal ions from aqueous solutions on Nafion 117 membrane , "Desalination, 249, 677-681 (2009)).

[Reaction Scheme 1]

Scheme 2

는 상기 화학식 1의 이오노머의 백본(backbone)을 나타내고, M⁺은 1가 금속 이온을, M^{2 +}는 2가 금속 이온을 나타내며, 상기 반응식 1 및 2는 상기 화학식 1의 이오노머에 포함된 술폰기 중 어느 하나의 술폰기가 M⁺ 또는 M^{2 +}와 반응하는 메커니즘을 나타낸다.In Schemes 1 and 2,

Represents a backbone of the ionomer of Formula 1, M ⁺ represents a monovalent metal ion, M ^{2 +} represents a divalent metal ion, and Schemes 1 and 2 are sulfone groups included in the ionomer of Formula 1 It represents a mechanism by which the sulfone group of either reacts with M ⁺ or M ^{2 +} .

In addition, the sulfonic acid group of the ionomer including the copolymer including the structural unit represented by Chemical Formula 1 adsorbs moisture in the electrolyte. The sulfonic acid group in the ionomer may contain a large amount of water by hydrogen bonding with H ₂ O, H ₃ O ⁺ and the like.

The content of the ionomer including the copolymer including the structural unit represented by Formula 1 may be about 0.1 to about 10 parts by weight based on 100 parts by weight of the active material. The ionomer content may be suitable for performing the beneficial functions described above by being located on the surface of the active material without disturbing the role of the active material when the ionomer is in the above range.

According to another embodiment of the present invention, a lithium secondary battery includes an electrode and a nonaqueous electrolyte including an ionomer including a copolymer including the structural unit represented by Formula 1 as described above.

The electrode may be an anode or a cathode.

The lithium secondary battery may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of separator and electrolyte used, and may be classified into a cylindrical shape, a square shape, a coin type, a pouch type, and the like, Depending on the size, it can be divided into bulk type and thin film type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

1 is an exploded perspective view of a lithium secondary battery according to one embodiment. 1, the lithium secondary battery 100 has a cylindrical shape and includes a cathode 112, a cathode 114, a separator 113 disposed between the cathode 112 and the anode 114, An electrolyte 114 (not shown), an electrolyte (not shown) impregnated into the separator 113, a battery container 120, and a sealing member 140 for sealing the battery container 120. The lithium secondary battery 100 is configured by stacking the negative electrode 112, the separator 113, and the positive electrode 114 in order, and then storing the lithium secondary battery 100 in the battery container 120 in a state wound in a spiral shape.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative active material. The negative electrode active material layer may also include an ionomer including a copolymer including the structural unit represented by Chemical Formula 1, and the detailed description is as described above.

The anode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the alloy of the lithium metal include lithium and metals of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, or Sn. Alloys can be used.

Examples of materials capable of doping and undoping lithium include Si, SiO _x (0 <x <2), Si-C composites, and Si-Q alloys (wherein Q is an alkali metal, an alkaline earth metal, and a group 13 to 16 element). , A transition metal, a rare earth element or a combination thereof, not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, an alkaline earth metal, an element of Group 13-16, a transition metal, A rare earth element or a combination thereof, not Sn), and at least one of these and SiO ₂ may be mixed and used. Specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof is mentioned.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and optionally may further include a conductive material.

The binder adheres the anode active material particles to each other well, and also serves to adhere the anode active material to the current collector well, and representative examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, and carboxylation. Polyvinylchloride, polyvinylfluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic ray Tied styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and may be used as long as it is an electronic conductive material without causing chemical change in the battery to be constructed. Examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, and ketjen black. Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam (foam), copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

The positive electrode includes a current collector and a cathode active material layer formed on the current collector. The positive electrode active material layer may also include an ionomer including a copolymer including the structural unit represented by Chemical Formula 1, and the detailed description thereof is as described above.

As the cathode active material, a compound (lithiated intercalation compound) capable of reversible intercalation and deintercalation of lithium may be used. Specifically, one or more of complex oxides of metal and lithium of cobalt, manganese, nickel or a combination thereof may be used, and specific examples thereof may be a compound represented by any one of the following formulas. _{Li a A 1 - b R b} D 2 ( in the above formula, 0.90 ≤ a ≤ 1.8 and 0 ≤ b ≤ 0.5); _{Li a E 1 - b R b} O 2 - ( in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and _{0 ≤ c ≤ 0.05) c D} c; _{LiE 2 - b R b O 4} - ( in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) c D c; _{Li a Ni 1 -b- c Co b} R c D α ( wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, ≤ c ≤ 0.05, and a 0 0 <α ≤ 2); Li _a Ni _{1- b c} Co _b R _c O _{2 -?} Z _? Wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b - c} Co _b R _c O _{2 -α} Z ₂ , wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2; Li _a Ni _{1 -b - c} Mn _b R _c D _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _{1 -b - c} Mn _b R _c O _{2 -α} Z _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05 and 0 <α <2); Li _a Ni _{1 -b - c} Mn _b R _c O _{2 -α} Z ₂ (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05 and 0 <α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, and 0.001 ≦ d ≦ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and 0.001 ≦ e ≦ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may include an oxide of a coating element, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming process may use any coating method as long as it does not adversely affect the physical properties of the positive electrode active material by using such elements in the compound (for example, spray coating, dipping, etc.). Details that will be well understood by those in the field will be omitted.

For example, in the case of using a lithium manganese oxide as the positive electrode active material, it may not be preferable in terms of lifespan characteristics, the lithium manganese ion ionomer containing a copolymer containing the structural unit represented by the formula (1) Inclusion with oxides can significantly improve lifespan characteristics.

The cathode active material layer also includes a binder and a conductive material.

The binder adheres positively to the positive electrode active material particles, and also serves to adhere the positive electrode active material to the current collector well, and examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and polyvinyl. Chloride, carboxylated polyvinylchloride, polyvinylfluoride, polymer comprising ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- Butadiene rubber, acrylic styrene-butadiene rubber, epoxy resin, nylon and the like can be used, but is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

As the current collector, Al may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are each prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. N-methylpyrrolidone may be used as the solvent, but is not limited thereto.

The electrolyte contains a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC) and the like can be used, and the ester solvent is methyl acetate, ethyl acetate, n-propyl acetate, methyl propionate, ethyl propionate, γ- Butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol solvent, and as the aprotic solvent, R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, Nitriles such as a bond aromatic ring or ether bonds), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolane, and the like.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, the cyclic carbonate and the chain carbonate may be mixed and used in a volume ratio of about 1: 1 to about 1: 9, so that the performance of the electrolyte may be excellent.

The non-aqueous organic solvent may further include the aromatic hydrocarbon organic solvent in the carbonate solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1: 1 to about 30: 1.

As the aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound of Formula 3 may be used.

(3)

In Formula 3, R ₁ to R ₆ are each independently hydrogen, halogen, C1 to C10 alkyl group, C1 to C10 haloalkyl group, or a combination thereof.

The aromatic hydrocarbon organic solvent is benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2, 4-trichlorobenzene, iodobenzene, 1,2-dioodobenzene, 1,3-dioodobenzene, 1,4-dioiobenzene, 1,2,3-triiodobenzene, 1,2,4 -Triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 -Trichlorotoluene, iodotoluene, 1,2-dioodotoluene, 1,3-dioodotoluene, 1,4-diaodotol Ene, 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, or may be a combination thereof.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate compound of Formula 4 to improve battery life.

[Formula 4]

In Formula 4, R ₇ and R ₈ are each independently hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a fluoroalkyl group of C1 to C5, and at least one of R ₇ and R ₈ Is a halogen group, cyano group (CN), nitro group (NO ₂ ) or a fluoroalkyl group of C1 to C5.

Representative examples of the ethylene carbonate compounds include difluoro ethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, and the like. Can be. When the vinylene carbonate or the ethylene carbonate-based compound is further used, the amount thereof may be appropriately adjusted to improve life.

The lithium salt is dissolved in the non-aqueous organic solvent, acts as a source of lithium ions in the battery to enable the operation of the basic lithium secondary battery, and serves to promote the movement of lithium ions between the positive electrode and the negative electrode to be. Representative examples of the lithium salt are LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y +1} SO ₂ ), where x and y are natural numbers, LiCl, LiI, LiB (C ₂ O ₄ ) ₂ (lithium bis (oxalato) borate (LiBOB) or combinations thereof The lithium salt may be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is included in the above range, the electrolyte has an appropriate conductivity and viscosity. It can exhibit excellent electrolyte performance, and lithium ions can move effectively.

The separator 113 separates the negative electrode 112 and the positive electrode 114 and provides a moving passage for lithium ions, and any separator can be used as long as it is commonly used in a lithium battery. In other words, those having low resistance to ion migration of the electrolyte and excellent electrolyte-wetting ability can be used. For example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in a nonwoven or woven form. For example, a polyolefin-based polymer separator such as polyethylene, polypropylene and the like is mainly used for a lithium ion battery, and a coated separator containing a ceramic component or a polymer substance may be used for heat resistance or mechanical strength, Structure.

Hereinafter, examples and comparative examples of the present invention will be described. Such following examples are only examples of the present invention, and the present invention is not limited to the following examples.

[Example]

Example  One

A graphite active material, an aramid binder, and Nafion 117 (DuPont) were mixed in water at a weight ratio of 94: 5.5: 0.5 to prepare a negative electrode active material slurry. A negative electrode plate was prepared.

Comparative example  One

The battery was manufactured by the same production method as in Example 1, and Nafion was not added when the negative electrode active material slurry was prepared.

Example  2

An 18650 circular battery was manufactured using the negative electrode plate prepared in Example 1 above. LiMn ₂ O ₄ was used as the positive electrode, and a separator was inserted and wound in the middle in the form as shown in FIG. 1, inserted into a can, followed by injecting and sealing an electrolyte solution to complete a battery. Electrolyte was used EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) = 3/4/3 (volume ratio) and contains 5 vol% FEC (fluoroethylene carbonate) additive.

Example  3

In Example 2, Nafion117 (DuPont) was added to prepare a cathode slurry without adding Nafion to the cathode. The positive electrode composition ratio is 96: 1.5: 2: 0.5 in the order of LiMn ₂ O ₄ , a binder, a conductive agent, and Nafion 117 (DuPont), and the other manufacturing method is the same as in Example 2.

Example  4

In preparing the negative electrode active material slurry in Example 2, Nafion was prepared, and the negative electrode active material slurry was coated on the current collector of the negative electrode to form a negative electrode active material layer having a thickness of 100 μm. The Nafion 117 (DuPont) solution was spray-coated to a thickness of 300 nm on the anode active material layer. The Nafion 117 (DuPont) solution was prepared to be a Nafion 117 (DuPont) solution at a concentration of 15 wt% using a mixed solvent of 1-propanol and water. Otherwise, an 18650 circular battery was manufactured in the same manner as in Example 2.

Example  5

In preparing the positive electrode active material slurry in Example 3, Nafion was prepared, and the positive electrode active material slurry was coated on the current collector of the positive electrode to form a positive electrode active material layer having a thickness of 100 μm. Nafion 117 (DuPont) solution was spray-coated to a thickness of 300 nm on the cathode active material layer. The Nafion 117 (DuPont) solution was prepared to be a Nafion 117 (DuPont) solution at a concentration of 15 wt% using a mixed solvent of 1-propanol and water. Otherwise, an 18650 circular battery was manufactured in the same manner as in Example 3.

Comparative example  2

An 18650 circular battery was manufactured in the same manner as in Example 1, except that the negative electrode active material prepared in Preparation Example 2 was used.

As shown in FIG. 4, high-temperature standing life characteristics of the lithium secondary batteries of Examples 2 to 5 and Comparative Example 2 prepared as described above were evaluated.

The high temperature left life evaluation is a method for accelerating the life of the battery to shorten the evaluation period, but to determine the tendency of the battery to deteriorate at high temperature. The method for evaluating the high temperature leaving life is to measure the capacity reduction rate with respect to the initial capacity at regular intervals (10 days) while leaving the produced battery in a charger / discharger maintained at 60 ° C. The time period to measure is determined by the deterioration tendency of the battery.

100: lithium secondary battery 112: negative electrode
113: separator 114: anode
120: battery container 140: sealing member

Claims (13)

Active material; And
A copolymer comprising a structural unit represented by the formula (1)
Electrode for a lithium secondary battery comprising:
[Formula 1]

In this formula,
A is selected from the group consisting of -O- (CFR _f3 -CFR _f4 )-,-(CFR _f5 -CFR _f6 ) _-and combinations thereof,
R _f1 to R _f6 are each independently selected from the group consisting of fluorine, C1 to C4 alkyl, and fluorinated C1 to C4 alkyl,
x and y are each independently an integer of 1-100,000. The method of claim 1,
A lithium secondary battery electrode in which the structural unit represented by Formula 1 is represented by Formula 2 below:
(2)

In this formula,
x is an integer from 3 to 20,
y is an integer from 1 to 10,
z is an integer from 1 to 10. The method of claim 1,
The active material is a lithium secondary battery electrode containing a positive electrode active material. The method of claim 3,
The cathode active material is a lithium secondary battery electrode comprising a lithium manganese oxide. The method of claim 1,
The active material is a lithium secondary battery electrode containing a negative electrode active material. The method of claim 1,
The content of the copolymer is a lithium secondary battery electrode of 0.1 to 10 parts by weight based on 100 parts by weight of the active material. The method of claim 1,
The copolymer is a lithium secondary battery electrode comprising a material selected from the group consisting of Nafion N1110, Nafion N117, Nafion N115, Nafion NR-212, Nafion NR-211, Nafion XL-100, Nafion NR50 1100 EW and combinations thereof. The method of claim 1,
The electrode is a lithium secondary battery electrode comprising an active material layer comprising a mixture of the copolymer and the active material. The method of claim 1,
The electrode includes an active material layer and a coating layer,
The coating layer is a lithium secondary battery electrode that is formed by coating the copolymer directly on the active material layer. 10. The method of claim 9,
The active material layer is a lithium secondary battery electrode comprising a mixture of the copolymer and the active material. The method of claim 10,
The copolymer is an electrode for a lithium secondary battery in which the active material layer is present to increase the concentration toward the interface with the coating layer in the. -According to claim 9,
The thickness of the coating layer is a lithium secondary battery electrode of 0.1% to 10% of the active material layer. The first electrode according to any one of claims 1 to 12;
A second electrode;
Separator; And
Electrolyte
&Lt; / RTI &gt;

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